layout/generic/StickyScrollContainer.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /**
   8  * compute sticky positioning, both during reflow and when the scrolling
   9  * container scrolls
  10  */
  11
  12 #ifndef StickyScrollContainer_h
  13 #define StickyScrollContainer_h
  14
  15 #include "nsPoint.h"
  16 #include "nsTArray.h"
  17 #include "nsIScrollPositionListener.h"
  18
  19 struct nsRect;
  20 class nsIFrame;
  21 class nsIScrollableFrame;
  22
  23 namespace mozilla {
  24
  25 class StickyScrollContainer MOZ_FINAL : public nsIScrollPositionListener
  26 {
  27 public:
  28   /**
  29    * Find (and create if necessary) the StickyScrollContainer associated with
  30    * the scroll container of the given frame, if a scroll container exists.
  31    */
  32   static StickyScrollContainer* GetStickyScrollContainerForFrame(nsIFrame* aFrame);
  33
  34   /**
  35    * Find the StickyScrollContainer associated with the given scroll frame,
  36    * if it exists.
  37    */
  38   static StickyScrollContainer* GetStickyScrollContainerForScrollFrame(nsIFrame* aScrollFrame);
  39
  40   /**
  41    * aFrame may have moved into or out of a scroll frame's frame subtree.
  42    */
  43   static void NotifyReparentedFrameAcrossScrollFrameBoundary(nsIFrame* aFrame,
  44                                                              nsIFrame* aOldParent);
  45
  46   void AddFrame(nsIFrame* aFrame) {
  47     mFrames.AppendElement(aFrame);
  48   }
  49   void RemoveFrame(nsIFrame* aFrame) {
  50     mFrames.RemoveElement(aFrame);
  51   }
  52
  53   nsIScrollableFrame* ScrollFrame() const {
  54     return mScrollFrame;
  55   }
  56
  57   // Compute the offsets for a sticky position element
  58   static void ComputeStickyOffsets(nsIFrame* aFrame);
  59
  60   /**
  61    * Compute the position of a sticky positioned frame, based on information
  62    * stored in its properties along with our scroll frame and scroll position.
  63    */
  64   nsPoint ComputePosition(nsIFrame* aFrame) const;
  65
  66   /**
  67    * Compute where a frame should not scroll with the page, represented by the
  68    * difference of two rectangles.
  69    */
  70   void GetScrollRanges(nsIFrame* aFrame, nsRect* aOuter, nsRect* aInner) const;
  71
  72   /**
  73    * Compute and set the position of a frame and its following continuations.
  74    */
  75   void PositionContinuations(nsIFrame* aFrame);
  76
  77   /**
  78    * Compute and set the position of all sticky frames, given the current
  79    * scroll position of the scroll frame. If not in reflow, aSubtreeRoot should
  80    * be null; otherwise, overflow-area updates will be limited to not affect
  81    * aSubtreeRoot or its ancestors.
  82    */
  83   void UpdatePositions(nsPoint aScrollPosition, nsIFrame* aSubtreeRoot);
  84
  85   // nsIScrollPositionListener
  86   virtual void ScrollPositionWillChange(nscoord aX, nscoord aY) MOZ_OVERRIDE;
  87   virtual void ScrollPositionDidChange(nscoord aX, nscoord aY) MOZ_OVERRIDE;
  88
  89 private:
  90   explicit StickyScrollContainer(nsIScrollableFrame* aScrollFrame);
  91   ~StickyScrollContainer();
  92
  93   /**
  94    * Compute two rectangles that determine sticky positioning: |aStick|, based
  95    * on the scroll container, and |aContain|, based on the containing block.
  96    * Sticky positioning keeps the frame position (its upper-left corner) always
  97    * within |aContain| and secondarily within |aStick|.
  98    */
  99   void ComputeStickyLimits(nsIFrame* aFrame, nsRect* aStick,
 100                            nsRect* aContain) const;
 101
 102   friend void DestroyStickyScrollContainer(void* aPropertyValue);
 103
 104   nsIScrollableFrame* const mScrollFrame;
 105   nsTArray<nsIFrame*> mFrames;
 106   nsPoint mScrollPosition;
 107 };
 108
 109 } // namespace mozilla
 110
 111 #endif /* StickyScrollContainer_h */